1. Field of the Invention
The present invention relates to a method for diagnosis of gastrointestinal tract disorders by measurement of the level of lactoferrin, myeloperoxidase or polymorphonuclear leucocyte elastase in feces. Particularly, a screening test method for colorectal cancer by measurement of the level of lactoferrin or myeloperoxidase in feces by immunoassay and by measurement of the level of whole-sized lactoferrin by immunoassay utilizing monoclonal antibody. 2. Description of the Prior Art
In various kinds of gastrointestinal tract diseases such as inflammatory gastrointestinal disorders and gastrointestinal cancer, intestinal chronic bleeding is observed in inflammation neoplasia at the mucous membrane, or protein leaking in gastrointestinal tract is observed due to permeability disorder of capillary blood vessel or pressure raise of lymphoduct.
In order to diagnose the gastrointestinal tract diseases, the fecal occult blood test method has most been used for screening of gastrointestinal tract diseases with bleeding, especially for mass screening of colorectal cancer.
Among the fecal occult blood test, the guaiac method is the most widely used and the method utilizes the peroxidase activity of the heme in hemoglobin, hence not only human hemoglobin in feces, but also hemoglobin from animal and fish meat or special vegetable is detected by this method. Since human hemoglobin is not detected specifically by the Guaiac method, subjects are required to follow a special diet in order to prevent the occurrence of false positive results. Moreover, it has been difficult to increase the sensitivity of this method.
In recent years, as the fecal occult blood test, immunological methods using an anti-human hemoglobin antibody e.g. enzyme immunoassay or latex agglutination has been developed. These methods have high specificity and high sensitivity for human hemoglobin and do not require a special diet. However, the stability of hemoglobin in feces is low, which sometimes induces false negative results. Other problems in the diagnosis of gastrointestinal tract disease by fecal occult blood test are false positive readings resulting from the admixture of blood from sources other than the gastrointestinal tract, for example, blood from damaged blood vessels of the anus and physiological loss of blood.
Now it has been found that an amount of a neutrophil leucocyte releasing substance in feces, particularly, lactoferrin, myeloperoxidase or polymorphonuclear leucocyte elastase, have a good relation to the diagnosis of inflammatory gastrointestinal disorders, colon polyp or colorectal cancer.
A method for diagnosis of inflammatory diarrhea by latex agglutination assay or enzyme-linked immunosorbent assay using a fecal leucocyte releasing substance, specifically lactoferrin as a marker, was disclosed in U.S. Pat. No. 5,124,252, which is however directed to distinguish whether it is the invasive and inflammatory diarrhea usually caused by bacteria such as Shigella, Salmonella or Clostridium. The above invention does not relate to diagnosis for inflammatory gastrointestinal disorders, colon polyp and colorectal cancer which are not caused by invasion or infection.
As the result of an extensive study to overcome the above drawbacks and problems as seen in the known method, now we have developed a new method for diagnosis of inflammatory gastrointestinal tract disorders, colon polyp or colorectal cancer.